<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Circle Border Animation</title>
    <style>
        .circle {
            width: 200px;
            height: 200px;
            border-radius: 50%;
            background: conic-gradient(black 0deg, black 360deg);
            border: 10px solid transparent;
            box-sizing: border-box;
            animation: reduceBorder 90s linear forwards;
        }

        @keyframes reduceBorder {
            0% {
                background: conic-gradient(black 0deg, black 360deg);
            }
            100% {
                background: conic-gradient(black 0deg, black 324deg, white 324deg, white 360deg);
            }
        }
    </style>
</head>
<body>
    <div class="circle"></div>

    <script>
        document.addEventListener('DOMContentLoaded', function() {
            const circle = document.querySelector('.circle');
            let currentAngle = 360;

            setInterval(function() {
                currentAngle -= 4; // 每秒减少4度，相当于每秒减少1%
                circle.style.background = `conic-gradient(black 0deg, black ${currentAngle}deg, white ${currentAngle}deg, white 360deg)`;
            }, 1000);
        });
    </script>
</body>
</html>